1. Field of the Invention
The present invention relates to a vent grid utilized in an electronic apparatus, for example.
2. Description of the Prior Art
A computer includes an enclosure. A vent grid is incorporated in the back wall of the enclosure, for example. The vent grid defines a matrix of square openings, for example. A cooling fan is enclosed inside the enclosure. The cooling fan serves to generate airflow circulating through the enclosure. The airflow absorbs heat from a motherboard likewise enclosed inside the enclosure. The heated airflow is discharged out of the enclosure through the openings of the vent grid. The circulation of the airflow in this manner contributes to establishment of a lower temperature inside the enclosure.
An electronic circuit element such as a central processing unit, CPU, is mounted on the motherboard. The central processing unit radiates electromagnetic wave. An increased clock frequency of the central processing unit causes leakage of the electromagnetic wave out of the enclosure through the openings of the vent grid. The leaked electromagnetic wave sometimes causes erroneous performance of the peripherals. If the area of the individual opening is sufficiently reduced as compared with the wavelength of the electromagnetic wave, the leakage of the electromagnetic wave can be prevented. However, a reduced area of the opening leads to a deteriorated efficiency of the cooling fan and cooling performance.
Moreover, the vent grid is usually made of an electrically-conductive material such as an iron plate. When the electromagnetic wave radiating from the electronic circuit element acts on the vent grid, flow of electric current is generated in the vent grid. The electromagnetic wave is induced in the vent grid in response to the flow of the electric current. The electromagnetic wave passes directly through the vent grid while the electromagnetic wave is radiated from the vent grid. The generation of the electromagnetic wave should be suppressed.